Field of the Invention
One disclosed aspect of the embodiments relates to a printing apparatus configured to perform printing, a control method for the printing apparatus, and a storage medium.
More specifically, a disclosed aspect of the embodiments relates to a printing apparatus configured to perform printing and a control method for the printing apparatus.
Description of the Related Art
There are two methods for reading a document such as an optical system moving method and a feeding-reading method. With the optical system moving method, while an optical system is being moved, it reads a document placed at a fixed document position on a platen glass. One technique is called First Copy Out Time (FCOT). FCOT indicates how much time it takes a printing apparatus to read the first page of a document and output that page onto a sheet based on generated image data. With the feeding-reading method, while a document placed on a document tray is being conveyed by an automatic document feeder (ADF), an optical system fixed at a position reads the document.
In a digital copy machine discussed in Japanese Patent Application Laid-Open No. 9-261387, a scanner sequentially reads an image of each document fed by an Automatic Document Feeder (ADF) and stores generated image data in an image memory (this operation is referred to as an image read operation). Upon completion of the image read operation, this digital copy machine outputs the image data stored in the image memory to a printer to form an image on a sheet (this operation is referred to as an image forming operation). When the first document is fed by the ADF, this digital copy machine stores image data generated by reading an image of the document with the scanner in the image memory and then outputs the image data without compression to the printer to form an image on a sheet. For example, if a document jam occurs in the ADF during execution of the image read operation on the third document by the scanner and the image forming operation on the image data of the first document by the printer, the digital copy machine stops only the image read operation. Even after the image read operation stops, the digital copy machine continues the image forming operation on the image data of the document already stored in the image memory.
With a printing apparatus in which the speed for storing image data in an image memory through document reading is higher than the speed for reading image data from the image memory for printing, it is desirable to perform the image read operation and the image forming operation in parallel from the viewpoint of shortening processing time.
Accordingly, the printing apparatus reads image data of a document to be read (hereinafter referred to as a target document) from the storage device before image data for one page of the target document has been stored in the storage device and then performs printing based on the read image data (hereinafter this mode is referred to as a copy parallel processing mode). While this mode improves the speed of processing, there may be some situations that produce undesirable results. One such situation is the generation of indefinite data caused by an interruption as will be explained in the following.
If an interruption factor occurs before image data for one page of the target document has been stored in the storage device, the remaining image data of the target document is not stored in the storage device. For example, if an interruption factor such as a document jam occurs during conveyance of the target document, the conveyance of the document stops and therefore the remaining image of the target document is not read. In this case, since a video signal of the remaining image of the document is not input to the controller unit of the printing apparatus, the remaining image data of the document is not stored in the storage device. Therefore, indefinite data stored in the storage area of the storage device in which the remaining image data of the document is to be stored is not overwritten by the remaining image data of the document, i.e., indefinite data remains in the storage area.
For this reason, if an interruption factor occurs before image data for one page of the target document has been stored in the storage device, the printing apparatus reads indefinite data remaining in the storage area of the storage device in which the remaining image data of the target document is to be stored. Some examples of indefinite data include random data stored in the image memory when data stored in the image memory is cleared, and data stored in the image memory during execution of another job (e.g., a print job received from an external apparatus via a network, a FAX reception job, etc.).
Then, the printing apparatus performs printing based on the read indefinite data. If this indefinite data is random data unexpected by a user, the printing apparatus will perform printing based on the random data. In such a case, when the user sees a printed sheet (printed product), the user may get confused at the unexpected data. On the other hand, if this indefinite data is data of a different user's job that cannot essentially be accessed by the user, the printing apparatus will perform printing based on the data of the different user's job. In such a case, when the user sees a printed sheet (printed product), the user will get to know the data of the different user's job that cannot essentially be accessed.